1. Field of the Invention
The invention relates to a process for the production of silicone coatings and silicone moldings from photocrosslinkable silicone mixtures.
2. Background Art
In many applications in the electrical and electronics industry, it is desired to work with silicone elastomers which have as low a viscosity as possible. This is the case typically when either very narrow geometrical regions of a component are to be filled with casting compound, the surface to be coated or cast must be wet as quickly as possible, or material is to be applied in very thin layers. The latter case may be desirable in particular for cost reasons.
Commercially available, low-viscosity, solvent-free coating materials reach low processing viscosities in the neighborhood of 100 mPa·s (Dow Corning HC-2000: 130 mPa·s; Dow Corning 3-1965: 110 mPa·s; “Information über Dow Corning Schutzlacke [Information about Dow Corning protective lacquers], 1999-2005”). Mixtures having even lower viscosities could potentially be prepared by using oligomeric alkyl- and alkenylsiloxanes. However, this cannot be realized in practice since the mechanical properties of such mixtures no longer meet the requirements for use.
Nevertheless, lacquers (urethane- or epoxy-based) having viscosities of 10 mPa·s or less are used for the circuit board coating application. Such low viscosities can be achieved with conventional silicone mixtures only by using organic solvents, which however is not expedient for reasons of workplace safety and environmental protection.